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Seed longevity, the capacity to remain alive during dry storage, is pivotal to germination performance and essential to preserve genetic diversity. It is acquired during late maturation concomitantly with the seed degreening and de-differentiation of chloroplasts into colorless, non-photosynthetic plastids called eoplasts. Since chlorophyll retention leads to poor seed performance upon sowing, these processes are important for seed vigor. However, how they are regulated and connected to the acquisition of seed longevity remains poorly understood. Here, we show that such a role is provided by ABSCISIC ACID INSENSITIVE 4 in the legume Medicago truncatula. Mature seeds of Mtabi4 mutants contained more chlorophyll than wild-type seeds and exhibited a 75% reduction in longevity and reduced dormancy. MtABI4 was necessary to stimulate eoplast formation as evidenced by the significant delay in the dismantlement of photosystem II during maturation of mutant seeds. Mtabi4 seeds also exhibited transcriptional deregulation of genes associated with retrograde signaling and transcriptional control of plastid encoded genes. Longevity was restored when Mtabi4 seeds developed in darkness, suggesting that shutdown of photosynthesis during maturation rather than chlorophyll degradation per se is a requisite for the acquisition of longevity. Indeed, shelf life of stay green mutant seeds that retained chlorophyll was not affected. Thus, ABI4 plays a role in coordinating the dismantlement of chloroplasts during seed development to avoid damage and compromise seed longevity acquisition. Analysis of Mtabi4 Mtabi5 double mutants showed synergistic effects on chlorophyll retention and longevity, suggesting that they act via parallel pathways.

Introduction: Patients with chronic obstructive pulmonary disease (COPD) may be prone to stress urinary incontinence (SUI) due to the repetitive stresses induced by coughing on the pelvic floor. The objective of this study is to determine the prevalence of incontinence in these patients. Method: Cross-sectional study carried out on 60 COPD subjects aged over 18 recruited in five hospitals in Brussels. Two questionnaires were completed to assess respiratory and pelvic parameters. Results: To compare the characteristics of patients with or without SUI, the sample was divided into two groups: a COPD group with symptoms of SUI (n = 17) and a COPD group without symptoms of SUI (n = 43). Subjects in the groups had equivalent characteristics. The prevalence of urinary incontinence was 28.3% with 58.82% of women and 41.18% of men. Conclusion: It is important for healthcare professionals to include a questioning of UI in the assessment of COPD patients with the aim of overall management. Level of evidence: 3., SCOPUS: ar.j, info:eu-repo/semantics/published

End of March 2019, the Luxembourg Institute of Luxembourg (LIST) organized the 12th Central European Diatom (thereafter CED) Meeting in Belvaux, Grand Duchy of Luxembourg (Ector et al. 2019) with t...

Diatoms are feedstock for the production of sustainable biocommodities, including biofuel. The biochemical characterization of newly isolated or genetically modified strains is seminal to identify the strains that display interesting features for both research and industrial applications. Biochemical quantification of organic macromolecules cellular quotas are time-consuming methodologies which often require large amount of biological sample. Vibrational spectroscopy is an essential tool applied in several fields of research. A Fourier transform infrared (FTIR) microscopy-based imaging protocol was developed for the simultaneous cellular quota quantification of lipids, carbohydrates, and proteins of the diatom Phaeodactylum tricornutum. The low amount of sample required for the quantification allows the high throughput quantification on small volume cultures. A proof of concept was performed (1) on nitrogen-starved experimental cultures and (2) on three different P. tricornutum wild-type strains. The results are supported by the observation in situ of lipid droplets by confocal and brightfield microscopy. The results show that major differences exist in the regulation of lipid metabolism between ecotypes of P. tricornutum.

Microalgae have been recognized as one of the most efficient microorganisms to remediate industrial effluents. Among microalgae diatoms are silica shelled unicellular eukaryotes, found in all types of water bodies and flourish very well even in wastewater. They have their silica cell wall made up of nano arrayed pores arranged in a uniform fashion. Therefore, they act as smart nanocontainers to adsorb various trace metals, dyes, polymers, and drugs which are hazardous to human as well to aquatic life. The beautiful nanoarchitecture in diatoms allows them to easily bind to ligands of choice to form a nanocomposite structure with the pollutants which can be a chemical or biological component. Such naturally available diatom nanomaterials are economical and highly sensitive compared to manmade artificial silica nanomaterials to help in facile removal of the toxic pollutants from wastewater. This review is thus focused on employing diatoms to remediate various pollutants such as heavy metals, dyes, hydrocarbons detected in the wastewater. It also includes different microalgae as biosensors for determination of pollutants in effluents and the perspectives for nanotechnological applications in the field of remediating pollutants through microalgae. The review also discusses in length the hurdles and perspectives of employing microalgae in wastewater remediation.

Cell disruption is very important for the value-added biocompounds (VAB) to come out from microalgae. Among the most demanding microalgae at industrial level, diatoms and Haematococcus pluvialis have hooked the race. However, they at the same time face difficulty in their cell wall disruption for the VAB to come out as it is very rigid and thick. This is among the major barrier in construction of diatom solar panels for biofuel production. Different diatom walls experience different shear forces for harvesting its biomass. This results in raising the overall cost of photobioreactors controlling their growth and recovery of biomass and VAB. In order to lower the cost, the cell wall of microalgae needs to milk the metabolites without itself getting sacrificed. The current review in depth discusses the techniques to break the cell wall of microalgae especially diatoms and Haematococcus using nanotechnological approaches without lysing the cell. The research gaps, commercial applications, and future research directions have been identified and discussed to strengthen the environmental and economical sustainability.

Photosynthetic microbial fuel cells (PMFCs) with microalgae have huge potential for treating wastewater while simultaneously converting light energy into electrical energy. The efficiency of such cells is directly dependent upon algal growth, which depends upon light intensity. Higher light intensity results in increased potential as well as enhancement in generation of biomass rich in biopolymers. Such biopolymers are produced either by microbes at anode and algae at cathode or vice versa. The biopolymers recovered from these biological sources can be added in wastewater alone or in combination with nanomaterials to act as nanoabsorbents. These nanoabsorbents further increase the efficiency of PMFC by removing the pollutants like metals and dyes. In this review firstly the effect of different light intensities on the growth of microalgae, importance of diatoms in a PMFC and their impact on PMFCs efficiencies have been narrated. Secondly recovery of biopolymers from different biological sources and their role in removal of metals, dyes along with its impact on circular bioeconomy have been discussed. Thereafter bottlenecks and future perspectives in this field of research have been narrated.

The formation of different intracellular compartments is necessary for the physical separation of various biochemical reactions, their products as well as different ions by barriers made up by memb...

Perovskite solar cells (PVSCs) convert solar energy into electrical energy. Current study employs fabrication of PVSCs using calcium titanate (CaTiO3) prepared by co-precipitation of TiO2 nanoparticle (NP) and CaCO3 NP with later synthesized from mollusc shell. Furthermore, frustules of diatom, Nitzschia palea were used to prepare silica doped CaTiO3 (Si-CaTiO3) nanocomposite. CaTiO3 NP and Si-CaTiO3 nanocomposites film were made on fluorine doped tin oxide (FTO) glass plate using spin coater separately for two different kinds of PVSCs tested at different intensities of light. The perovskite materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX) spectroscopy. Thickness of the film was measured by profilometer. The maximum power density (PDmax) of CaTiO3 made PVSCs was 0.235 mW/m2 under white LED light and 0.041 mW/m2 in broad spectrum light. Whereas, PDmax of PVSCs with Si-CaTiO3 was higher about 0.0083 mW/m2 in broad spectrum light and was 0.0039 mW/m2 in white LED light. This is due to the fact that CaTiO3 allowed blue and red light in broad spectrum to pass through it without being absorbed compared to white LED light which gets reflected. On the offset, in PVSC made of Si-CaTiO3 since diatoms frustules are made up of nanoporous architecture it increases the overall porosity of PVSC making them potentially more efficient in broad spectrum of light compared to white LED light.

SUMMARYPhotosynthetic oxygen evolution by photosystem II requires water supply into the chloroplast to reach the thylakoid lumen. A rapid water flow is also required into the chloroplast for optimal oxygen evolution and to overcome osmotic stress. The mechanisms governing water transport in chloroplasts are largely unexplored. Previous proteomics indicated the presence of three aquaporins from the tonoplast intrinsic protein (TIP) family, TIP1;1, TIP1;2 and TIP2;1, in chloroplast membranes of Arabidopsis thaliana. Here we revisited their location and studied their role in chloroplasts. Localization experiments indicated that TIP2;1 resides in the thylakoid, whereas TIP1;2 is present in both thylakoid and envelope membranes. Mutants lacking TIP1;2 and/or TIP2;1 did not display a macroscopic phenotype when grown under standard conditions. The mutant chloroplasts and thylakoids underwent less volume changes than the corresponding wild type preparations upon osmotic treatment and in the light. Significantly reduced rates of photosynthetic electron transport were obtained in the mutant leaves, with implications on the CO2 fixation rates. However, electron transport rates did not significantly differ between mutants and wild type when isolated thylakoids were examined. Less acidification of the thylakoid lumen was measured in mutants thylakoids, resulting in a slower induction of delta pH-dependent photoprotective mechanisms. These results identify TIP1;2 and TIP2;1 as chloroplast proteins and highlight their importance for osmoregulation and optimal photosynthesis. A third aquaporin, TIP1;1, is present in the chloroplast envelope, and may play role in photosynthesis under excessive light conditions, as based on the weak photosynthetic phenotype of its mutant.

Carotenoids are one the most frequently coloured molecules encountered in our environment. Beside their colouring effect, carotenoids are famous for their photoprotection and antioxidant properties. Because carotenoids conserve their properties in vitro, the interest for these natural molecules increased. To satisfy the growing demand for carotenoids, new sources are searched and microalgae emerged as organisms with a very high potential. Using the most recent publications, we established that the production of carotenoids by microalgae is a tailor-made process requiring the proper biological and environmental factors. The optimization of the biotechnological processes aiming at producing carotenoids from microalgae requires a deeper knowledge in the regulation of the carotenoid biosynthetic pathways, that might be used to engineer microalgal strains.

In this chapter we review the current knowledge about channels and transporters in the envelope and thylakoid membranes of chloroplasts from algae. These proteins mediate the exchange of ions and metabolites between the cytosol and the chloroplast stroma and between the different chloroplast sub-compartments. In secondarily-evolved algae, three or four envelope membranes surround the chloroplast, making more complex the exchange of ions and metabolites. Despite the importance of transport proteins for the optimal functioning of the chloroplast in algae, and that many land plant homologues have been predicted, experimental evidence and molecular characterization are missing in most cases. Most chloroplast transporters have been identified in the green alga Chlamydomonas reinhardtii, residing in the envelope membranes, and participate in carbon acquisition and metabolism. Only a few identified algal transporters are located in the thylakoid membrane and play roles in ion transport. The presence of genes for putative transporters in green algae, red algae, diatoms, glaucophytes and cryptophytes is discussed, and their roles in the chloroplast are proposed. A greater knowledge in this important field is required because algae represent a potential source of biomass and valuable metabolites for industry, medicine and agriculture.

International audience; Microalgae are photosynthetic microorganisms that produce numerous bioactive molecules that can be used as food supplement to prevent chronic disease installation. Indeed, they produce phycobiliproteins, polysaccharides, lipids, carotenoids and sterolic compounds. The use of microalgae in human nutrition provide a mixture of these molecules with synergistic effect. The aim of this review is to present the specific roles played by the xanthophylls, and specifically astaxanthin and fucoxanthin, two high added value carotenoids, and by microalgal phytosterols such as β-sitosterol, campesterol and stigmasterol on several cell mechanisms involved in the prevention of cardiometabolic diseases and cancers. This review explains how these microalgal molecules modulate cell signaling pathways involved in carbohydrate and lipid metabolisms, inflammation, apoptosis, invasion and metastasis. Xanthophylls and phytosterols are involved in the reduction of inflammatory markers in relation with the regulation of the c-Jun N-terminal kinases and nuclear factor-kappa B signaling pathways, and suppression of production of pro-inflammatory mediators. Xanthophylls act on glucose and lipid metabolisms via both the upregulation of peroxisome proliferator-activated receptors (PPARs) and glucose transporters and its effects on the expression of enzymes involved in fatty acid synthesis and cholesterol metabolism. Their anti-cancer effects are related to the induction of intrinsic apoptosis due to down-regulation of key regulatory kinases. The anti-angiogenesis, anti-proliferative and anti-invasive effects are correlated with decreased production of endothelial growth factors and of matrix metalloproteinases. Phytosterols have a major role on cholesterol absorption via modification of the activities of Niemann-Pick C1 like 1 and ATP-binding cassette transporters and on cholesterol esterification. Their action are also related with the modulation of PPARs and sterol regulatory element-binding protein-1 activities.

Chloroplasts are endosymbiotic organelles and play crucial roles in energy supply and metabolism of eukaryotic photosynthetic organisms (algae and land plants). They harbor channels and transporters in the envelope and thylakoid membranes, mediating the exchange of ions and metabolites with the cytosol and the chloroplast stroma and between the different chloroplast subcompartments. In secondarily evolved algae, three or four envelope membranes surround the chloroplast, making more complex the exchange of ions and metabolites. Despite the importance of transport proteins for the optimal functioning of the chloroplast in algae, and that many land plant homologues have been predicted, experimental evidence and molecular characterization are missing in most cases. Here, we provide an overview of the current knowledge about ion and metabolite transport in the chloroplast from algae. The main aspects reviewed are localization and activity of the transport proteins from algae and/or of homologues from other organisms including land plants. Most chloroplast transporters were identified in the green alga Chlamydomonas reinhardtii, reside in the envelope and participate in carbon acquisition and metabolism. Only a few identified algal transporters are located in the thylakoid membrane and play role in ion transport. The presence of genes for putative transporters in green algae, red algae, diatoms, glaucophytes and cryptophytes is discussed, and roles in the chloroplast are suggested. A deep knowledge in this field is required because algae represent a potential source of biomass and valuable metabolites for industry, medicine and agriculture. Electronic supplementary material The online version of this article (10.1007/s00018-018-2793-0) contains supplementary material, which is available to authorized users.

Wastewater management and its treatment have revolutionized the industry sector into many innovative techniques. However, the cost of recycling via chemical treatment has major issues especially in economically poor sectors. On the offset, one of the most viable and economical techniques to clean wastewater is by growing microalgae in it. Since wastewater is rich in nitrates, phosphates and other trace elements, the environment is suitable for the growth of microalgae. On the other side, the cost of harvesting microalgae for its secondary metabolites is burgeoning. While simultaneously growing of microalgae in photobioreactors requires regular feeding of the nutrients and maintenance which increases the cost of operation and hence cost of its end products. The growth of microalgae in waste waters makes the process not only economical but they also manufacture more amounts of value added products. However, harvesting of these values added products is still a cumbersome task. On the offset, it has been observed that pretreating the microalgal biomass with ultrasonication allows easy oozing of the secondary metabolites like oil, proteins, carbohydrates and methane at much lower cost than that required for their extraction. Among microalgae diatoms are more robust and have immense crude oil and are rich in various value added products. However, due to their thick silica walls they do not ooze the metabolites until the mechanical force on their walls reaches certain threshold energy. In this review recycling of wastewater using microalgae and its pretreatment via ultrasonication with special reference to diatoms is critically discussed. Perspectives on circular bioeconomy and knowledge gaps for employing microalgae to recycle wastewater have been comprehensively narrated.

Photocatalytic disinfection of drinking water is habitually performed by an ultraviolet source that epitomizes only 4% of the total solar energy, increasing the cost and prolonging the whole process. Therefore, currently, functionalized nanomaterials are developed, which can pave the way for the utilization of visible light, thereby speeding up the disinfection process in a cost-effective manner. In this study, we synthesized titanium dioxide (anatase) and bismuth vanadate (monoclinic) nanoparticles through the sol-gel technique. This is followed by a simple-blending process with graphene oxide (GO) to produce nanocomposites, such as GO/titanium dioxide (GOT) and bismuth vanadate (GOB), by varying the ratios of nanostructures accordingly and confirmed by different characterization techniques. 1.5 GOT and 1.5 GOB (nanocomposites of 1.5 wt.% GO with TiO2 and BiVO4 nanoparticles) showed enhanced inactivation efficiency of Escherichia coli (E.coli) K12 (model microorganism). Hydroxyl ( OH) and superoxide (O2 −) radicals were found to be responsible for producing reactive oxygen species (ROS), playing a crucial role in photocatalytic disinfection, which was evaluated through scavenger study. We attained disinfection of E.coli K12 having a concentration of 10 7 CFU/mL with a smaller quantity of 1.5 GOT (1.05 g/L), obtaining 99.9 % (3 log units) of inactivity in 30 min. while for 1.5 GOB (0.1 g/L) resulting in 89 % (

Diatoms adapt to changing environmental conditions in very efficient ways. Among the mechanisms that can be activated, the reorientation of carbon metabolism is crucial because it allows the storage of energy into energy-dense molecules, typically lipids. Beside their roles in physiology, lipids are commercially interesting compounds. Therefore studies dealing with this topic are relevant for both basic and applied science. Although the molecular mechanisms involved in the reorientation of carbon metabolism as a response to a deficiency in nutrients such as nitrogen or phosphorus has been partially elucidated, the impacts of carbon availability on the implementation of the reorientation mechanisms remain unclear. Indeed, it has not been determined if the same types of mechanisms are activated under carbon and other nutrient deficiencies or limitations. The first aim of this work was to get insights into the physiological, biological and molecular processes triggered by progressive carbon starvation in the model diatom Phaeodactylum tricornutum. The second aim was to investigate the effects of the growth light intensity on these processes. For such a purpose three different photon flux densities 30, 300, and 1000 μmol photons m-2 s-1 were used. The results presented here demonstrate that under carbon limitation, diatom cells still reorient carbon metabolism toward either phosphoenolpyruvate or pyruvate, which serves as a hub for the production of more complex molecules. The distribution of carbon atoms between the different pathways was partially affected by the growth photon flux density because low light (LL) provides conditions for the accumulation of chrysolaminarin, while medium light mostly stimulated lipid synthesis. A significant increase in the amount of proteins was observed under high light (HL).

Marine microalgae are known to be a source of bioactive molecules of interest to human health, such as n-3 polyunsaturated fatty acids (n-3 PUFAs) and carotenoids. The fact that some of these natural compounds are known to exhibit anti-inflammatory, antioxidant, anti-proliferative, and apoptosis-inducing effects, demonstrates their potential use in preventing cancers and cardiovascular diseases (CVDs). Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon (PAH), is an ubiquitous environmental pollutant known to contribute to the development or aggravation of human diseases, such as cancer, CVDs, and immune dysfunction. Most of these deleterious effects are related to the activation of the polycyclic aromatic hydrocarbon receptor (AhR). In this context, two ethanolic microalgal extracts with concentrations of 0.1 to 5 &micro, g/mL are tested, Ostreoccoccus tauri (OT) and Phaeodactylum tricornutum (PT), in order to evaluate and compare their potential effects towards B[a]P-induced toxicity in endothelial HMEC-1 cells. Our results indicate that the OT extract can influence the toxicity of B[a]P. Indeed, apoptosis and the production of extracellular vesicles were decreased, likely through the reduction of the expression of CYP1A1, a B[a]P bioactivation enzyme. Furthermore, the B[a]P-induced expression of the inflammatory cytokines IL-8 and IL1-&beta, was reduced. The PT extract only inhibited the expression of the B[a]P-induced cytokine IL-8 expression. The OT extract therefore seems to be a good candidate for counteracting the B[a]P toxicity.

This study aims to employ a pulsed electric field (PEF) treatment for the biocompatible (non-destructive) extraction of proteins from living cells of the green microalga Haematococcus pluvialis. Using a field strength of 1 kV cm-1, we achieved the extraction of 10.2 µg protein per mL of culture , which corresponded to 46% of the total amount of proteins that could be extracted by complete destructive extraction (i.e. the grinding of biomass with glass beads). We found that the extraction yield was not improved by stronger field strengths and was not dependent on the pulse frequency. A biocompatibility index (BI) was defined as the relative abundance of cells that remained alive after the PEF treatment. This index relied on measurements of several physiological parameters after a PEF treatment. This way found that at 1 kV cm-1 that cultures recovered after 72 h. Therefore, these PEF conditions constituted a good compromise between protein extraction efficiency and culture survival. To characterize the PEF treatment further at a molecular level, mass spectrometry-based proteomics analyses of PEF-prepared extracts was used. This led to the identification of 52 electro-extracted proteins. Of these, only 16 proteins were identified when proteins were extracted with PEF at 0.5 cm-1. They belong to core metabolism, stress response and cell movement. Unassigned proteins were also extracted. Their physiological implications and possible utilization in food as alimentary complements are discussed.

During arbuscular mycorrhizal symbiosis, arbuscule-containing root cortex cells display a proliferation of plastids, a feature usually ascribed to an increased plant anabolism despite the lack of studies focusing on purified root plastids. In this study, we investigated mycorrhiza-induced changes in plastidic pathways by performing a label-free comparative subcellular quantitative proteomic analysis targeted on plastid-enriched fractions isolated from Medicago truncatula roots, coupled to a cytological analysis of plastid structure. We identified 490 root plastid protein candidates, among which 79 changed in abundance upon mycorrhization, as inferred from spectral counting. According to cross-species sequence homology searches, the mycorrhiza-responsive proteome was enriched in proteins experimentally localized in thylakoids, whereas it was depleted of proteins ascribed predominantly to amyloplasts. Consistently, the analysis of plastid morphology using transmission electron microscopy indicated that starch depletion associated with the proliferation of membrane-free and tubular membrane-containing plastids was a feature specific to arbusculated cells. The loss of enzymes involved in carbon/nitrogen assimilation and provision of reducing power, coupled to macromolecule degradation events in the plastid-enriched fraction of mycorrhizal roots that paralleled lack of starch accumulation in arbusculated cells, lead us to propose that arbuscule functioning elicits a nutrient starvation and an oxidative stress signature that may prime arbuscule breakdown.

Diatoms are nature's nanobot because they can be described as cells in a glass house. Three-dimensional nanobio-engineered frustules of diatoms have vast applications in nanomaterials and bio-photonics. The amorphous silica of diatom frustules is not a good semiconductor, but when coated with titanium dioxide (TiO2), the semiconducting efficiency of the frustules becomes adequate for use in numerous device applications, including solar cells. The metabolic incorporation of titanium dioxide nanoparticles in the diatom frustules is primarily used for the construction of titanium nanotubes. In the present study, TiO2 was metabolically inserted by a two-stage cultivation process and its incorporation in the diatom frustules was studied by spectroscopic and atomic force microscopic methods. It was found that diatom frustules metabolically inserted with nanostructured TiO2 by a two-stage cultivation in f/2 medium could replace nanostructured surface doping with titanium in dye-sensitized solar cells for heat and electricity production. The DSSC made from the titanium-doped diatom frustule has a power efficiency almost double (9.45%) that of the simple DSSC (4.20%) without any diatom frustule metabolically inserted with TiO2. Alternatively, these nanoarray diatom containing tubes may also be used for the construction of novel dye-sensitized solar cells, which may help in oozing lipids from living diatom cells, such as in algal cells, for the generation of an electric current.

International audience

International audience; Classical methods, used for large scale treatments such as mechanical or chemical extractions, affect the integrity of extracted cytosolic protein by releasing proteases contained in vacuoles. Our previous experiments on flow processes electroextraction on yeasts proved that pulsed electric field technology allows preserving the integrity of released cytosolic proteins, by not affecting vacuole membranes. Furthermore, large cell culture volumes are easily treated by the flow technology. Based on this previous knowledge, we developed a new protocol in order to electro-extract total cytoplasmic proteins from microalgae (Nannochloropsis salina, Chlorella vulgaris and Haematococcus pluvialis). Given that induction of electropermeabilization is under the control of target cell size, as the mean diameter for N. salina is only 2.5 μm, we used repetitive 2 ms long pulses of alternating polarities with stronger field strengths than previously described for yeasts. The electric treatment was followed by a 24 h incubation period in a salty buffer. The amount of total protein release was observed by a classical Bradford assay. A more accurate evaluation of protein release was obtained by SDS-PAGE. Similar results were obtained with C. vulgaris and H. pluvialis under milder electrical conditions as expected from their larger size.

The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2) to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program). Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a) development of alternative methods to extract and harvest high added value compounds; (b) design of photobioreactors; (c) biodiversity and (d) stress physiology, illustrated with original results dealing with oleaginous diatoms.

Diatoms are single cells that can be regarded as nature's unique nanofabrication factories. They are “nanobioreactors” producing an extraordinary diversity of patterns and structures on their silica shells that can be used for synthesizing fascinating products. The nanostructured surface of diatoms serves as a template for the formation of biomimetic patterns from the nanoscale up to the microscale through various lithographic techniques. The resultant biologically inspired nanostructures can be further used as biosensors in explosives detection, and biomedical and optical devices etc. The surface of the silica of both living and fossilised diatoms can also be doped with a variety of oxides, metals and polymers for use in photovoltaic solar cells, lubricants, paints and pharmaceutical drug delivery carriers. Extant since the Jurassic era, diatoms are a major source of crude oil. Living diatoms can be used to produce biofuel. Construction of devices that milk diatoms without sacrificing them may make it possible to construct diatom solar panels (DSPs) to generate oil.

Diatoms are microalgae that arose over the last 100 Myr, thus phylogenetically constituting a relatively recent group of organisms. Analysis of microfossils that can be traced through geological time, as well as their contributions to seafloor sediments and fossil fuel reserves, demonstrates that diatoms have played a crucial role during this time. The review by Benoiston et al . [1] in this issue combines the current information on the evolution and biogeochemical functions of diatoms over time. Paleoecological data contain information for evaluating genetic variation through past climate changes, going back thousands of years in time [2]. In their review, Godhe & Reynardson [3] suggest the adoption of multiple strains of individual species for refining our understanding of the carbon metabolism and its variation within and between species. Diatoms are photosynthetic organisms using the energy of the Sun to build up organic molecules via CO2 fixation (primary production). For a long time, land plants have been supposed to be the main primary producers, however, recent estimations consider the contribution of algae to be as high as that of land plants [4]. The key process of the photosynthetic Calvin–Bensson–Bassham cycle is the fixation of CO2 onto ribulose-1,5-bisphosphate, mediated by the catalytic enzyme activity of RuBisCO. This reaction yields 3-phosphoglycerates, which immediately are converted to triose phosphates that are required to regenerate ribulose-1,5-bisphosphate. The contribution by Jensen et al . [5] reviews the regulation of the Calvin–Benson–Bassham cycle in diatoms, presenting a regulation process that is based on transcriptional regulation. This finding contrasts with land plants, in which the Calvin–Benson–Bassham is mostly regulated at the enzymatic level. Because a high local CO2 partial pressure in the close vicinity of the RuBisCO is vital to avoid photorespiration, …

Arbuscular mycorrhizas (AM) are the most common symbiotic associations between a plant's root compartment and fungi. They provide nutritional benefit (mostly inorganic phosphate [Pi]), leading to improved growth, and nonnutritional benefits, including defense responses to environmental cues throughout the host plant, which, in return, delivers carbohydrates to the symbiont. However, how transcriptional and metabolic changes occurring in leaves of AM plants differ from those induced by Pi fertilization is poorly understood. We investigated systemic changes in the leaves of mycorrhized Medicago truncatula in conditions with no improved Pi status and compared them with those induced by high-Pi treatment in nonmycorrhized plants. Microarray-based genome-wide profiling indicated up-regulation by mycorrhization of genes involved in flavonoid, terpenoid, jasmonic acid (JA), and abscisic acid (ABA) biosynthesis as well as enhanced expression of MYC2, the master regulator of JA-dependent responses. Accordingly, total anthocyanins and flavonoids increased, and most flavonoid species were enriched in AM leaves. Both the AM and Pi treatments corepressed iron homeostasis genes, resulting in lower levels of available iron in leaves. In addition, higher levels of cytokinins were found in leaves of AM- and Pi-treated plants, whereas the level of ABA was increased specifically in AM leaves. Foliar treatment of nonmycorrhized plants with either ABA or JA induced the up-regulation of MYC2, but only JA also induced the up-regulation of flavonoid and terpenoid biosynthetic genes. Based on these results, we propose that mycorrhization and Pi fertilization share cytokinin-mediated improved shoot growth, whereas enhanced ABA biosynthesis and JA-regulated flavonoid and terpenoid biosynthesis in leaves are specific to mycorrhization.

Background Since the industrial revolution, the consumption of processed food increased dramatically. During processing, food material loses many of its natural properties. Objective The simple restoration of the original properties of the processed food as well as fortification require food supplementation with compounds prepared chemically or of natural origin. The observations that natural food additives are safer and better accepted by consumers than synthetic ones have strongly increased the demand for natural compounds. Because some of them have only a low abundance or are even rare, their market price can be very high. This is the case for most carotenoids of natural origin to which this review is dedicated. The increasing demand for food additives of natural origin contributes to an accelerated depletion of traditional natural resources already threatened by intensive agriculture and pollution. To overcome these difficulties and satisfy the demand, alternative sources for natural carotenoids have to be found. In this context, photosynthetic microalgae present a very high potential because they contain carotenoids and are able to produce particular carotenoids under stress. Their potential also resides in the fact that only ten thousands of microalgal strains have been described while hundred thousands of species are predicted to exist. Carotenoids have been known for ages for their antioxidant and coloring properties, and a large body of evidence has been accumulated about their health potential. Conclusion This review summarizes both the medicinal and food industry applications of microalgae with emphasis on the former. In addition, traditional and alternative microalgal sources used for industrial carotenoid extraction, the chemical and physical properties, the biosynthesis and the localization of carotenoids in algae are also briefly discussed.

In this study, we investigated the responses of Phaeodactylum tricornutum cells acclimated to 300 µmol m−2 s−1 photon flux density to an increase (1000 µmol m−2 s−1) or decrease (30 µmol m−2 s−1) in photon flux densities. The light shift occurred abruptly after 5 days of growth and the acclimation to new conditions was followed during the next 6 days at the physiological and molecular levels. The molecular data reflect a rearrangement of carbon metabolism towards the production of phosphoenolpyruvic acid (PEP) and/or pyruvate. These intermediates were used differently by the cell as a function of the photon flux density: under low light, photosynthesis was depressed while respiration was increased. Under high light, lipids and proteins accumulated. Of great interest, under high light, the genes coding for the synthesis of aromatic amino acids and phenolic compounds were upregulated suggesting that the shikimate pathway was activated.

International audience; In urban agriculture, plant growth is limited by the availability of light. Light emitting diodes (LED) could provide specific quality and quantity of light overcoming existing limitations for normal plant growth. However, there have been very few investigations on the applications of LED in incubators and plant growth chambers. The devices fabricated in this study, were lighted with 100 % red, 100 % blue, 70 % red plus 30 % blue, or 100 % white LED. We cultivated Mentha piperita, Mentha spicata and Mentha longifolia, lentil, basil, and four ornamentals to test the effect of various LED lights on plants productivity compared with field and greenhouse conditions. Our results show that 70/30 % red-blue LED light increased Mentha essential oil yield up to four times along with increases in plant photosynthesis and fresh weight compared with field condition. The red-blue LED incubator also led to a better growth of lentil and basil and to higher flower buds and less days to flowering for pot flowers versus greenhouse conditions. Our findings demonstrate that LED could improve economic characteristics of plant species by probably stimulating plant metabolism.

Diatoms are unicellular brown algae with silica walls. They synthesize and store oil in the form of lipid droplets. Much of the crude oil we use comes from fossil diatoms. Extracting oil from living diatoms, as from any other algae, is a cumbersome and cost ineffective process requiring heavy input of energy. We constructed a resonating microfluidic chamber of dimensions 30 mm × 30 mm × 200 μm which is made up of a silicon wafer (orientation ) attached to a piezoelectric disc. The diatoms in −0.5 mL culture medium containing −2.5 × 10 /ml cells are siphoned with a syringe pump at the rate of 10 μl/min at one end of the chamber. The device is further connected to a function generator and oscilloscope to maintain a resonance frequency of 250 KHz and a static voltage of 500 mV. The resonating device is made to resonate for 2 to 20 min. The resonance frequency causes the diatoms to exocytose oil while retaining cell integrity. The number of cells that are were alive at all stages has been found to be 45–50% which can be used for reviving the cells and hence for oozing of oil again. The resonating microfluidic chamber is thus a prototype for a diatom biofuel solar panel which in the presence of sunlight and small energy input milks oil from diatoms.

Equipe DAVEM = Diversité et Adaptation de la Vigne et des Espèces Méditerranéennes; International audience; Background and Aims Condensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta. Methods Light microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine-glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions. Key Results and Conclusions The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.

International audience; Phytoplankton is acknowledged to be a very diverse source of bioactive molecules. These compounds play physiological roles that allow cells to deal with changes of the environmental constrains. For example, the diversity of light harvesting pigments allows efficient photosynthesis at different depths in the seawater column. Identically, lipid composition of cell membranes can vary according to environmental factors. This, together with the heterogenous evolutionary origin of taxa, makes the chemical diversity of phytoplankton compounds much larger than in terrestrial plants. This contribution is dedicated to pigments and lipids synthesized within or from plastids/photosynthetic membranes. It starts with a short review of cyanobacteria and microalgae phylogeny. Then the bioactivity of pigments and lipids (anti-oxidant, anti-inflammatory, anti-mutagenic, anti-cancer, anti-obesity, anti-allergic activities, and cardio-neuro-, hepato-and photoprotective effects), alone or in combination, is detailed. To increase the cellular production of bioactive compounds, specific culture conditions may be applied (e.g., high light intensity, nitrogen starvation). Regardless of the progress made in blue biotechnologies, OPEN ACCESS Mar. Drugs 2013, 11 3426 the production of bioactive compounds is still limited. However, some examples of large scale production are given, and perspectives are suggested in the final section.